Strain the tomatoes over a bowl and set the juice aside.

Place olive oil, tomatoes, garlic, onion, salt, pepper, parsley, (and red pepper flakes and grated Parmigiano if using) into the jug and attach the lid.

Select the chop program and turn to the coarse texture on the dial. Scrap down the sides if necessary.

Remove the measuring cup from the lid and select pulse on speed 1, then quickly increase to speed 5 or 6. Add 3-4 tablespoons of the reserved tomato juice through the lid opening to thin out the puree and allow the sauce to fully combine.

Add the butter 1 tablespoon at a time until mixed in and somewhat melted.

Adjust the seasoning to your liking.